Comment 2 for bug 993942

Hot fix for fresh installed Ubuntu 12.04 LTS (final):
1) download binary packages for unity 5.8.0 and libnux 5.8.0 from Launchpad.
  i386:
    http://launchpadlibrarian.net/98435767/unity_5.8.0-0ubuntu2_i386.deb
    http://launchpadlibrarian.net/98435770/unity-common_5.8.0-0ubuntu2_all.deb
    http://launchpadlibrarian.net/98435769/unity-services_5.8.0-0ubuntu2_i386.deb
    http://launchpadlibrarian.net/98435771/libunity-core-5.0-5_5.8.0-0ubuntu2_i386.deb
    http://launchpadlibrarian.net/98014262/libnux-2.0-0_2.8.0-0ubuntu1_i386.deb
    http://launchpadlibrarian.net/98014265/libnux-2.0-common_2.8.0-0ubuntu1_all.deb
  amd64:
    http://launchpadlibrarian.net/98434829/unity_5.8.0-0ubuntu2_amd64.deb
    http://launchpadlibrarian.net/98435770/unity-common_5.8.0-0ubuntu2_all.deb
    http://launchpadlibrarian.net/98434830/unity-services_5.8.0-0ubuntu2_amd64.deb
    http://launchpadlibrarian.net/98434831/libunity-core-5.0-5_5.8.0-0ubuntu2_amd64.deb
    http://launchpadlibrarian.net/98014032/libnux-2.0-0_2.8.0-0ubuntu1_amd64.deb
    http://launchpadlibrarian.net/98014265/libnux-2.0-common_2.8.0-0ubuntu1_all.deb
2) install packages using dpkg:
  dpkg -i unity*.deb libunity*.deb libnux*.deb
This will replace the existing packages with the old version. After rebooting, Unity is smooth and fast and causes reasonably low loads.

Don't forget to set the packages on hold using "dpkg --set-selections" so they won't be upgraded next time you start the update manager.